Evaluation of the toxicity of continuous infusion N-acetyl acysteine (NAC) in conjunction with high dose i.v. bolus interleukin-2 (IL-2) in the treatment of metastatic or unresectable renal cell carcinoma and malignant melanoma. This phase 1A trial will attempt to define the dose-limiting toxicity and maximal tolerated dose of NAC in conjunction with IL-2.